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MPG improved after adding 35s - wait what?

Jeepmarkjl

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I fully expected my MPG to decrease after adding 35s (no lift). Had the dealer recalibrate for the larger tire and I i double checked MPH comparing Speedo and variety of independent sources and it all checked out. I improved 1.5 more per Gallon. I didn't change the route or way I drive or any other weight reduction. So how is that possible? Was the Jeep originally calibrated wrong? Not complaining though.

BGF KO2 315s
No lift
No other changes
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MikeJLURubi

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I hope not. I am considering going to the same 35s very soon.
Have you had any negative issues?
 

Howardlv22

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im not exactly sure but if your jeep is new, a lot of jeeps need 1k-5k miles break in before reaching peak mpg performance and it might just be a timing coincidence. also, if your jeep is a diesel like mine, I went 37's and barely saw an mpg drop so 35's might just pair really well with the diesel etc.
 

multicam

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I wouldn’t jump to that conclusion without a huge sample size both before and after to account for all the variables that can affect efficiency. I also wouldn’t draw any conclusions unless you’re calculating it by hand (i.e. using miles for a tank divided by the total gallons put into the jeep, as opposed to the trip computer). Also- are you sure the recalibration is accurate? Like if they recalibrated it for 35” tires but yours are actually 34.125” when loaded, you may be traveling fewer miles in reality than your odometer says- which would throw off a MPG calculation.

Not trying to rain on your parade or anything, just expressing a few thoughts on the subject.
 

guarnibl

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I fully expected my MPG to decrease after adding 35s (no lift). Had the dealer recalibrate for the larger tire and I i double checked MPH comparing Speedo and variety of independent sources and it all checked out. I improved 1.5 more per Gallon. I didn't change the route or way I drive or any other weight reduction. So how is that possible? Was the Jeep originally calibrated wrong? Not complaining though.

BGF KO2 315s
No lift
No other changes
What were the stock tires? Falcon MTs (can you get these on the JLUR? I had them on my JTR)? If so that could be why as they're heavy SOBs.

My wife's 2 dr JLR is getting ~23 mpg on the stock KO2s (4 cyl).
 

aldo98229

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My JL came from the factory with the speedo mis-calibrated by 1.5 MPH. It got spot-on after I mounted 33” tires on it.

I have recalibrated the speedo with a Tazer after I got 35s.

Haven’t checked my current MPG, but I’ve noticed the automatic transmission hangs onto 4th thru 6th gears longer, refusing to get into higher gears until it hits freeway speeds. That alone is going to hurt my MPG
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